Jay Inslee at his office in Olympia, Washington on 24 January 2019.
Photograph: Ted S Warren/AP

Jay Inslee, the Democratic governor of Washington, has announced he is running for president, declaring himself the “only candidate who will make defeating climate change our nation’s number one priority”.

“We’re the first generation to feel the sting of climate change,” he said in a video announcing his launch. “And we’re the last who can do something about it.”

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Inslee, 68, is the first sitting governor to join the 2020 race, which has thus far been dominated by US senators. His announcement followed months of speculation over Inslee’s intentions and marks yet another entry into what is already a sprawling Democratic field.

Although lesser known on the national stage, Inslee has sought to cultivate an image as a warrior against climate change and hired multiple advisers who worked for Tom Steyer, the Democratic billionaire who recently ruled out a presidential run of his own.

While several other Democrats in the race have talked about the need to address climate change, Inslee is the only candidate who is running a campaign so singularly focused on the issue.

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“Our country’s next mission must be to rise up to the most urgent challenge of our time – defeating climate change,” he says in the launch video, which features old footage of him raising the issue on the floor if the House, where he served as a congressman for seven terms. “This crisis isn’t just a chart or graph any more. The impacts are being felt everywhere.”

Climate change has become an increasingly galvanizing force for Democrats, with grassroots groups and figures such as congresswoman Alexandria Ocasio-Cortez, the newly elected Democratic socialist from New York, calling for a “Green New Deal”.

His plan to impose a carbon tax was blocked by the state legislature, and a separate measure to impose a new fee on fossil fuel emissions through a state ballot initiative was rejected by voters in the 2018 midterm elections.

Under his leadership, Washington has become a bulwark of resistance against the Trump administration’s agenda. Washington was the first state to challenge the president’s travel ban. Washington also joined a coalition of left-leaning states to sue the Trump administration over its family separation policy and, more recently, to block the president’s emergency declaration to build a border wall without permission from Congress.

And in 2017, when Trump abruptly withdrew from the Paris climate accords, Inslee co-founded the US Climate Alliance, a bipartisan coalition of 21 states committed to meeting the goals of the pact.

As the chair of the Democratic Governors Association last year, Inslee traveled the country campaigning and raising money for his party’s gubernatorial candidates during the 2018 midterm elections. It proved a fruitful endeavor: Democrats flipped seven governors’ mansions in the November midterms, including high-profile victories in Michigan, Wisconsin, Nevada and Kansas.

In making his presidential bid official, Inslee joined a host of higher-profile Democratic contenders that include Senators Bernie Sanders of Vermont, Elizabeth Warren of Massachusetts, Kamala Harris of California, Kirsten Gillibrand of New York, Cory Booker of New Jersey and Amy Klobuchar of Minnesota.

The US representative from Hawaii, Tulsi Gabbard, the South Bend, Indiana, mayor, Pete Buttigieg, and the former San Antonio mayor Julián Castro are also vying for the top of the party’s 2020 ticket; and the former vice-president Joe Biden and former Texas congressman Beto O’Rourke are being closely watched for possible announcements in the coming days or weeks.

He is also likely to be joined in the race by the Montana governor, Steve Bullock, and former Colorado governor John Hickenlooper.

Given his lack of name recognition, Inslee barely registers in early polling , receiving 0% support in one national survey of Democratic hopefuls. The same poll showed Inslee at only 1% in the early battleground states of Iowa, New Hampshire, South Carolina and Nevada.

But after a year marked by devastating storms, wildfires and increasingly dire warnings from scientists, recent polling suggests Americans are more concerned than ever before about the consequences of global warming.

The Republican party reacted with disdain. Republican National Committee communications director Michael Ahrens said in a statement: “Jay Inslee’s chances of becoming president are exactly what he’s polling at: zero. His campaign will only force Democrats into embracing more extreme policies, like a carbon tax, which would kill jobs, raise energy prices, and disproportionately hurt working-class Americans.”